1. Technical Field
The disclosed technology pertains generally to analog filter circuits, and more particularly to programmable analog filter circuits.
2. Discussion
State-of-the-art reconfigurable or programmable receivers still rely on: (a) traditional continuous-time (CT), integration sampling (IS), or discrete-time (DT) active filters at baseband and (b) low-selectivity passive filters at Radio Frequency (RF).
The traditional continuous-time (CT) or discrete-time (DT) active filters at baseband have a number of drawbacks, including: (1) that sharp CT analog filters are costly to integrate on chip, and (2) DT filters require increased chip area and power to provide limited bandwidth re-configurability. Integration sampling (IS) offers clock-programmable bandwidth. However, this alternative suffers from a slow roll-off and requires additional CT and/or DT stages to achieve selectivity.
At RF, passive filters based on impedance translation offer some degree of bandpass frequency and bandwidth programmability, combined with a large dynamic range, which improves on traditional fixed RF filters. Such RF passive filters, however, have two main drawbacks: (1) very weak selectivity that necessitates the employment of costly active subsequent filtering stages, and (2) limited harmonic cancellation that limits the range of carrier frequency programmability.
Accordingly, a need exists for an analog filter design which can be readily implemented at low power consumption levels even while providing sharp selectivity and high programmability.